www.g-vo.org spectral analysis in the vo thomas rauch, iliya nickelt and the gavo and astrogrid-d...
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Spectral Analysis in the Spectral Analysis in the VOVO
Thomas Rauch, Iliya Nickeltand the GAVO and AstroGrid-D Teams
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Spectral Energy Distributions for Hot Spectral Energy Distributions for Hot StarsStars
Multi-Wavelength Astronomy & Virtual Observatory
The nebular information indicates that the spectrum of the star deviates considerably
from a blackbody. Author in
2008!
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Multi-Wavelength Astronomy & Virtual Observatory
they still use black bodies to simulate ionizing fluxes of hot stars …
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Stellar Spectra vs Black Stellar Spectra vs Black Body IIBody II
Multi-Wavelength Astronomy & Virtual Observatory
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NLTE Model NLTE Model AtmospheresAtmospheres
• all stars with spectral type B or earlier
• regarded as a domain of specialists• high computational times• atomic data
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C IV doublet
“optical” RBB 5 6, 6 8
C III singlet + triplet
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GAVO II ProjectGAVO II Project
• provide access to spectral energy distributions (SEDs) at three levels:– fast and easy
• unexperienced user, no detailed knowledge about the model-atmosphere code necessary
– individual• interested user, detailed analysis of special
objects
– experienced• define own model atoms, comparison of codes,
etc.
Multi-Wavelength Astronomy & Virtual Observatory
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VO Service TheoSSAVO Service TheoSSA
• based on the Tübingen NLTE Model Atmosphere Package TMAP, the GAVO Service TheoSSA provides
– Spectral Energy Distributions (SEDs)• TheoSSA
(http://vo.ari.uni-heidelberg.de/ssatr-0.01/TrSpectra.jsp?)
– Simulation Software• TMAW (http://astro.uni-tuebingen.de/~TMAW/TMAW.shtml)
– Atomic Data• TMAD (http://astro.uni-tuebingen.de/~rauch/TMAD/TMAD.html)
Multi-Wavelength Astronomy & Virtual Observatory
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Way to Reality in the 21Way to Reality in the 21stst CenturyCentury
– use SED grids• ready to use, interpolation
– calculate individual model atmospheres •Teff, log g, mass fraction {Xi}, i (H, He, C, N,
O)– standard model atoms
– create own atomic-data files, i (H - Ni), and calculate model atmospheres and SEDs
Multi-Wavelength Astronomy & Virtual Observatory
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TheoSSA request: Teff, log g, {Xi}
check GAVO database:requested parameters matched
within tolerance limits?
yes: offer existing SEDno: calculate new model and SEDs
and ingest into GAVO database
accept request exact parameters
TheoSSA – Model SEDs on TheoSSA – Model SEDs on
DemandDemand
IAAT databaseTeff, log g, {Xi}
modelsatomic data filefrequency grid
GAVO databaseTeff, log g, {Xi}
SEDs5 - 2000Å
2000 - 3000Å3000 - 55000Å
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TheoSSA Data BaseTheoSSA Data Base
• growing in time– newly calculated SEDs are automatically
ingested– meta data at ARI (Heidelberg)– SEDs etc. at IAAT (Tübingen)
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Calculation of SEDs Calculation of SEDs
• cpu time increases with number of considered elements
– 1 H+He+C+N+O model ≈ 1 day on a fast PC
– IAAT cluster: 4 models parallel
• calculation of SED grids– compute resources of AstroGrid-D
Multi-Wavelength Astronomy & Virtual Observatory
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Why use a Grid?Why use a Grid?
• scales according to demand– 1, 10, or 100 cores available at any time
• higher reliability• middleware offers additional options
– job monitoring, statistics, error handling
• TMAP is easy to compute – no interprocess-communication– no complex compilation, all libraries
present
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Technical DetailsTechnical Details
• AstroGrid-D uses the Globus Toolkit middleware (GT4)
• compute resources are retrieved from the MDS (monitoring and discovery service)
• the job is submitted using a JSDL template (Job Submission Description Language)
• data transfer uses gsiftp, the job staging process is based on GT4 web services (globusrun-ws)
• all written in a two-page shell scriptMulti-Wavelength Astronomy & Virtual Observatory
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Task Farming with GlobusTask Farming with Globus
GAVOservice
Data
base
Web Interface
Multi-Wavelength Astronomy & Virtual Observatory
model input
executable
JSDL template
list of resources(nodes available)
Job s
ub
mis
sion host
output
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In ProgressIn Progress
• analysis of ionized nebulae– MOCASSIN: 3D photoionization code
(Barbara Ercolano, UCL)
• “wind models”– HotBlast: expanding stellar atmospheres
(Lars Koesterke, TACC)
• automated spectral analysis (IAAT, ?)Multi-Wavelength Astronomy & Virtual Observatory
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ConclusionsConclusions
SEDs of hot compact stars are available in the VO – use them!
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